Liquid crystal display devices are very popular display devices used in applications such as televisions, personal computers, and PDAs because of their light and thin designs and low electrical power consumption. As apparent in particular from liquid crystal displays for televisions, a recent trend of liquid crystal displays is the rapidly increasing size. For larger-scale devices, the multi-domain vertical alignment (MVA) mode is suitable because devices of this mode can be produced with high yield and have a wide viewing angle regardless of how large the size is. The multi-domain vertical alignment mode aligns liquid crystal molecules vertically to a substrate surface while no voltage is applied, and provides a higher contrast ratio than the conventional twisted nematic (TN) mode.
In the case of the MVA mode, it is not alignment films but projections (ribs) made of an insulating material that control the tilt angle of liquid crystal molecules. Accordingly, this mode eliminates the need of an alignment treatment for alignment films and therefore eliminates the need of post-treatment such as washing because of the absence of static electricity and dust which may arise by rubbing or the like. Additionally, the variations in the initial angle of liquid crystal molecules are small, and this mode is effective in terms of simple production, improvement of yield, and reduction of costs.
Although the MVA mode does not require any alignment treatment, a base film corresponding to an alignment film is still necessary. Such a base film may have negative impact on the alignment of liquid crystal molecules when it has an uneven thickness or contains unnecessary matter therein, and another disadvantage is that additional processes and equipment costs for producing a base film are required. Considering these disadvantages, a mode that can eliminate such a base film as well is more preferable.
In recent years, this preference has directed interest towards a technique to make a pretilt angle which involves sealing a liquid crystal composition containing polymerizable components such as monomers or oligomers (hereinafter, referred to as monomers or the like) between substrates, and forming a polymer layer by polymerization of the monomers or the like while liquid crystal molecules are tilted with a voltage applied between substrates (e.g. Patent Literatures 1 and 2). Such a polymer layer aligns liquid crystal at certain pretilt angles even when no voltage is applied, and namely can maintain the orientation of the liquid crystal molecules without alignment films. The polymerization of monomers or the like can be accomplished by heat or light (e.g. ultraviolet) radiation.